I want to simulate the flow inside a Cyclone. The geometry is shown below:

Part of the air outlet tube is inside the cyclone, so the internal patch (wall) must be created.

I think there are 2 possible ways to do such job:

1) Import the Tetrahedral Mesh generated by GMSH, and then generated the inner walls of air outlet tube with createBaffles, but I didn't find any tutorials about how to generated curved surface (can not find detailed topoSet or setSet guide).

2) Import the Surface Mesh (STL) and utilize the snappyHexMesh to generate the internal cells. But how does snappyHexMesh snap the internal surface and convert it to patches? It's possible in OF 2.2.0 to do this, but could not find the proper examples.

... createBaffles, but I didn't find any tutorials about how to generated curved surface (can not find detailed topoSet or setSet guide).

Have a look at the "propeller"-tutorial.
tutorials/incompressible/pimpleDyMFoam/propeller

But: you wont get a proper baffle if the surface of the cylinder is not included in your tet-mesh (see the tutorial).

Quote:

Originally Posted by keepfit

2) Import the Surface Mesh (STL) and utilize the snappyHexMesh to generate the internal cells. But how does snappyHexMesh snap the internal surface and convert it to patches? It's possible in OF 2.2.0 to do this, but could not find the proper examples.

I would do like this:
- generate the stl of your cyclon
- generate a second stl of the part of the cylinder, that is inside your cyclone
- in the snappyHexMeshDict-file the cylinder.stl gets the attribute "inside" in the part of the surface refinement